Study: Couch potatoes are thriving around world, not just U.S.

Americans may have a reputation for being overweight, but a study shows… (Digital Vision )

Too many Americans may be overweight couch potatoes, but a new study finds that people in four other big countries are just as out of shape and sedentary as we are.

People in China and Brazil, in particular, are becoming more sedentary as those countries modernize, and residents of the United Kingdom are even more inactive than Americans, according to a study by researchers at the University of North Carolina at Chapel Hill.

The researchers used data from the 1960s onward to determine how much people move around in the course of their daily lives.

First, the study found, modern conveniences such as microwaves and dishwashers have reduced laborious household chores, and an increased reliance on cars has cut into walking. Second, the popularity of the Internet and computer games, coupled with expanded TV options, have led to a lot more sitting around indoors.

"We have understood for some time that children and adults in the United States are increasingly spending more time in front of televisions and in other sedentary activities such as playing computer games, using computers and texting on cellphones," Shu Wen Ng, the study’s senior author, said in a statement.

"This study shows that the same shifts have also occurred in China, India, Brazil and the United Kingdom," said Ng, a research assistant professor of nutrition at UNC's Gillings School of Global Public Health. "In fact, we find adults in the U.K. are more sedentary than those in the U.S."

The five countries studied represent nearly 3 billion people, or almost half the world's population, the study said.

Researchers relied on time-use studies in the five countries to track declines in physical activity over the decades. Using projections based on the data, the study predicts that the trend toward inactivity will intensify in the next two decades as more nations modernize and their work forces migrate away from physical labor and into office and service jobs.

By 2020, the study predicts, the average American will not expend a whole lot more energy in a typical day than someone who slept all day long. Using a physiological measure called metabolic equivalent of task (MET), the study predicts that Americans in 2020 will expend an average of 190 MET hours per week, compared to 151 MET hours per week expended by a person who slept 24 hours a day.

By contrast, a typical adult who spent 30 minutes a day in vigorous activity but otherwise had a desk job would expend between 240 and 265 MET hours a week.

People in the United Kingdom will reach the sedentary 190 MET level in 2030, followed closely behind by residents of China and Brazil, the study predicts. India's activity rates will not drop as quickly, the study said, because while well-to-do Indians have lifestyles similar to the British, millions of other Indians remain mired in poverty and perform menial, labor-intensive jobs.

The study's authors said lowered activity has profound implications for future health and human development worldwide. They called for global initiatives to study ways to promote activity, saying physically active children learn better and physically active adults live longer, healthier lives.

The study, "Time use and physical activity: a shift away from movement across the globe," will appear in the August issue of Obesity Reviews.